In automotive applications, there is a push for energy efficiency. Efficiencies can be gained for example, by having a water pump which is deactivated upon cold starting of an engine so that the engine can come up to the running temperature more quickly. Known systems for deactivating a water pump include a moveable cover which covers the vanes of the pump impeller when the water pump is not required. However, in such known systems, a hydraulic actuator has been typically used, requiring special seals for the actuator fluid, and or a separate pump for the actuator if the coolant being moved by the water pump is also used as the drive fluid for the actuator.
Additionally, as the water pump speed is directly correlated to the speed of the engine, the flow from a standard water pump is proportional to the engine speed. However, coolant requirements in an engine vary greatly based on many factors. With the known hydraulically actuated deactivatable water pumps, the controls do not allow for specific flow control levels so that the coolant flow can be optimized for efficient engine performance during the various operating conditions, and instead are designed for “off” or “on” operation.
It would be desirable to provide a less complex and more reliable actuator arrangement, and in particular a mechanically acting actuator that can be simply controlled and allow variable actuation, and in particular such an actuator for use in connection with a variable flow water pump in order to allow more precise flow control, while also maintaining a small space requirement, low weight, and low cost.